The long-term goals of the proposed research are to study the transport properties of the blood-retinal barrier system utilizing both in vivo and in vitro techniques. The immediate projects involve the collection of data on the sugar transport system in isolated pigment epithelial (PE) cells for kinetic analysis. From preliminary data, the transport of glucose in isolated PE cells appears to follow complex kinetics which may indicate the existence of more than one mechanism for glucose translocation across the PE cell membrane. The apparent transport kinetics of isolated PE tissue mounted as a membrane in a chamber will also be studied. The effects of transport and metabolic inhibitors on this system will be assessed as well as possible regulatory agents such as alpha and beta stimulators and cyclic nucleotide analogs. In vivo studies on the blood-retinal barrier are under investigation. These employ a method utilized in studies of the blood-brain barrier in small animals. This technique is referred to as the "internal water standard method" and permits the determination of the retinal uptake indices of different types of substrates. The retinal uptake indices can be utilized in obtaining apparent kinetic parameters of glucose transport.